Position measurement device, terminal provided therewith, and position measurement method

• US 6,763,302 B2
• Filed: 02/26/2003
• Issued: 07/13/2004
• Est. Priority Date: 09/18/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Mori, Shinichiro
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US10/373,052
• Publication Number:
  US 20030130792A1
• Time in Patent Office: 503 Days
• Field of Search: 701/207, 701/213, 701/214, 340/988, 342/357.01, 342/357.06, 342/357.08
• US Class Current: 701/213
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks

Abstract

A position measurement device measures a position even in the case where the number of satellites necessary for position measurement with GPS cannot be ensured. In the case where the number of satellites necessary for position measurement cannot be acquired, a first position measurement device measures the position by finding the displacement distance from the nearest position, on the basis of three-dimensional acceleration detected by a three-dimensional acceleration sensor.

Claims

1. An azimuth measurement device comprising:

a plurality of azimuth measuring units disposed in mutually separate locations and detecting respectively the intensities of magnetic fields, including at least geomagnetism, to measure azimuth; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism on the basis of a comparison of the intensities of magnetic fields detected by each of said plurality of azimuth measuring units.

2. The azimuth measurement device, according to claim 1, wherein said determining unit determines that no external magnetic fields are present in the case where the intensities of the magnetic fields detected by each of said plurality of azimuth measuring units are approximately the same, and determines that external magnetic fields are present in the case where there is a difference that is greater than or equal to a prescribed value in the intensities of said magnetic fields.

4. The azimuth measurement device according to claim 1, wherein the azimuth measurement device is portable and comprises a terminal.

3. An azimuth measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, equal to three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensities of magnetic fields, at least including geomagnetism;

a data storing unit for storing the geomagnetic intensities corresponding to a plurality of positions; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism at the position measured by said position measuring unit, on the basis of the intensity of the magnetic field detected by said azimuth measuring unit at said position and the geomagnetic intensity corresponding to said position, that is stored in said data storing unit.

5. A portable terminal having an azimuth measurement device, the azimuth measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, equal to three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensities of magnetic fields, at least including geomagnetism;

a data storing unit for storing the geomagnetic intensities corresponding to a plurality of positions; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism at the position measured by said position measuring unit, on the basis of the intensity of the magnetic field detected by said azimuth measuring unit at said position and the geomagnetic intensity corresponding to said position, that is stored in said data storing unit.

6. A communication system comprising a server and a terminal able to communicate with the server through a network,

wherein said terminal comprises:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point, on the basis of radio wave information received from a prescribed number, equal to three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensity of magnetic field, at least including geomagnetism; and

a first communicating unit for sending the position measured by said position measuring unit and the intensity of the magnetic field at that position to said server, and receiving a response from the server; and

wherein said server comprises;

a data storing unit for storing data of the geomagnetic intensities corresponding to a plurality of positions;

a determining unit for determining the presence of external magnetic fields other than geomagnetism at said position on the basis of said measured position and said magnetic field intensity sent from said terminal, and the geomagnetic intensity corresponding to the position stored in said data storing unit; and

a second communicating unit for receiving said position and said magnetic field intensity sent from said terminal, and returning, in response thereto, said determination results to said terminal.

7. A method for detecting external magnetic fields comprising the steps of:

detecting the intensities of the magnetic fields, at least including geomagnetism, using a plurality of magnetism detecting units disposed in mutually separate locations; and

determining the presence of external magnetic fields other than geomagnetism on the basis of a comparison of the intensities of the magnetic fields detected by each of said plurality of magnetism detecting units.

8. A method for detecting external magnetic fields comprising:

finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, equal to three or more, of satellites, and measuring the position of the measurement point;

detecting the intensities of magnetic fields, at least including geomagnetism; and

determining the presence of external magnetic fields other than geomagnetism at the position on the basis of a comparison of the intensities of the magnetic fields detected in said second step at the position measured in said first step, with the geomagnetic intensity corresponding to that position.